Well, that might take care of it eventually, something will eat them!
Seriously, put them in the coop at night, grab them off the fence after dark and put them in to roost to keep them safe and home them.
Maybe you need to build a bigger coop?
Then put something floppy, or a couple strands of...
Either fence them out of the garden....or put a 1 to 2 foot floppy section along the top of the fence, sometimes if you make the top of the fence unstable(if they pause on top of fence) that can keep them off it and inside.